During my 8 years of Linux on and off usage I have tried more distros than I have chocolate bars. Each one of my previous encounters meant that I had to spend at least 2 days configuring before I have a desktop that I was somewhat comfortable with. With Ubuntu Feisty Fawn's latest test beta --for the first time ever-- this was not the case. I was up and running with all the niceties I wanted within 2 hours.

Because it has extremely poor performance on large dirs and requires mutual ssh passwordless login setup which is far from user friendly.
Besides, no support for discovering computers in your neighborhood exits.
By the way, is there an easy way do integrate nfs/gnome vfs with avahi to have shares discovery?